U.S. patent number 6,684,143 [Application Number 10/115,839] was granted by the patent office on 2004-01-27 for method for controlling an automatic transmission and controller suitable for such a method.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Friedrich Graf, Tibor Kiss, Martin Lachmayr, Bernd Last, Stefan Lauer, Martin Manz, Stephan Pindl, Tanja Roy.
United States Patent |
6,684,143 |
Graf , et al. |
January 27, 2004 |
Method for controlling an automatic transmission and controller
suitable for such a method
Abstract
A method for controlling an automatic transmission in a drive
train of a motor vehicle having a transmission controller selecting
and shifting gears of the transmission includes determining a new
gear by reference to gear shift characteristic curves and
generating a gear shift instruction as soon as a working point of
the drive train exceeds a gear shift characteristic curve. The
transmission controller determines a new gear that is expected to
be engaged shortly. If the new gear differs from the current gear,
an initial phase of the gear shift is carried out and the gear
shift is completed as soon as the gear shift instruction has been
generated. The initial phase is carried out as soon as the working
point drops below a predefined distance from the gear shift
characteristic curve.
Inventors: |
Graf; Friedrich (Sinzing,
DE), Kiss; Tibor (Regensburg, DE),
Lachmayr; Martin (Regensburg, DE), Last; Bernd
(Donaustauf, DE), Lauer; Stefan (Pettendorf-Kneiting,
DE), Manz; Martin (Regensburg, DE), Pindl;
Stephan (Bad Abbach, DE), Roy; Tanja (Holzheim am
Forst, DE) |
Assignee: |
Siemens Aktiengesellschaft
(Munich, DE)
|
Family
ID: |
7680185 |
Appl.
No.: |
10/115,839 |
Filed: |
April 3, 2002 |
Foreign Application Priority Data
|
|
|
|
|
Apr 3, 2001 [DE] |
|
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101 16 545 |
|
Current U.S.
Class: |
701/51;
180/337 |
Current CPC
Class: |
F16H
61/0213 (20130101); F16H 61/08 (20130101); F16H
2306/18 (20130101); F16H 2059/003 (20130101); Y10T
477/688 (20150115); Y10T 477/6937 (20150115) |
Current International
Class: |
F16H
61/02 (20060101); F16H 61/08 (20060101); G06F
017/00 () |
Field of
Search: |
;701/51,53,64
;180/170,337,338 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Cuchlinski, Jr.; William A.
Assistant Examiner: Hernandez; Olga
Attorney, Agent or Firm: Greenberg; Laurence A. Stemer;
Werner H. Mayback; Gregory L.
Claims
We claim:
1. A method for controlling an automatic transmission in a drive
train of a motor vehicle having a transmission controller selecting
and shifting gears of the transmission, which comprises:
determining a new gear during a gear selection by referring to a
gear shift characteristic curve stored in a characteristic diagram;
generating a gear shift instruction to trigger a gear shift as soon
as a working point of the drive train exceeds a corresponding point
on the gear shift characteristic curve; determining, with the
transmission controller, a new gear expected to be engaged shortly
and carrying out an initial phase of the gear shift when the new
gear differs from the currently engaged gear and as soon as the
working point exceeds a pre-defined distance from the gear shift
characteristic curve; and completing a gear shift as soon as the
gear shift instruction has been generated.
2. The method according to claim 1, which further comprises storing
preselection characteristic curves running at the pre-defined
distance from the individual gear shift characteristic curves in
the characteristic diagram.
3. The method according to claim 2, which further comprises
calculating a distance between the preselection characteristic
curves and the gear shift characteristic curves as a function of a
transmission type.
4. The method according to claim 2, which further comprises
calculating a distance between the preselection characteristic
curves and the gear shift characteristic curves as a function of a
transmission type during ongoing operation.
5. The method according to claim 1, which further comprises
prohibiting a gear shift to a gear determined as being expected to
be engaged shortly if a dynamic correction of the gear shift
instruction has taken place.
6. The method according to claim 5, which further comprises
carrying out the prohibited gear shift as soon as the dynamic
correction of the gear shift instruction is eliminated.
7. The method according to claim 5, which further comprises setting
the suppressed new gear as being the new gear to be engaged
shortly.
8. The method according to claim 5, which further comprises setting
the suppressed new gear as being the new gear expected to be
engaged shortly.
9. The method according to claim 1, which further comprises
predicting an expected gear shift instruction by analyzing, in a
manual driving mode, a behavior of a driver of the motor vehicle
characteristic of a driving style.
10. A method for controlling an automatic transmission in a drive
train of a motor vehicle having a transmission controller selecting
and shifting gears of the transmission, which comprises:
determining a new gear during a gear selection by referring to a
gear shift characteristic curve stored in a characteristic diagram;
generating a gear shift instruction to trigger a gear shift as soon
as a working point of the drive train exceeds a corresponding point
on the gear shift characteristic curve; determining, with the
transmission controller, a new gear expected to be engaged shortly
and carrying out an initial phase of the gear shift as soon as the
working point exceeds a pre-defined distance from the gear shift
characteristic curve; and completing a gear shift as soon as the
gear shift instruction has been generated.
11. In an automatic transmission of a motor vehicle, the
transmission having gears, a transmission controller for
controlling a transmission ratio, comprising: a characteristic
diagram memory storing: transmission ratios to be set as a function
of: a torque; and a variable functionally associated with a speed
of the vehicle; gear shift characteristic curves; and preselection
characteristic curves lying at a predetermined distance from said
gear shift characteristic curves; and a processor programmed: to
signal an expected new gear to the transmission and to prepare a
gear shifting operation when a working point overshoots said
preselection characteristic curves; and to trigger a gear shifting
operation when the working point of the motor vehicle overshoots
the gear shift characteristic curves.
12. The controller according to claim 11, including: a gear
selector circuit for determining a new gear of the transmission,
said gear selector circuit connected to said processor; and a
transmission control unit connected to said processor and to said
gear selector circuit, said transmission control unit receiving a
new gear signal, preparing a gear shifting operation, and carrying
out a gear shift to the new gear as soon as the new gear determined
by said gear selector circuit differs from a currently engaged
gear.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for controlling an automatic
transmission in a drive train of a motor vehicle and a controller
for the automatic transmission of a motor vehicle. The method is
used to control an automatic transmission in a drive train of a
motor vehicle whose transmission controller carries out a gear
selection and a gear shift. A new gear is determined during the
gear selection by reference to a characteristic diagram and a new
gear that is expected to be engaged shortly is determined by its
transmission controller, an initial phase of the gear shift being
carried out when the new gear differs from the currently engaged
gear, and a gear shift being completed as soon as the gear shift
instruction has been generated.
German Patent DE 199 37 716 C1 discloses a method for controlling
an automatic transmission in a drive train of a motor vehicle. The
publication does not specify when or by which event the initial
phase of the gear shift is triggered.
German Published, Non-Prosecuted Patent Application DE 198 19 463
A1 discloses a method for controlling an automatic transmission in
a drive train of a motor vehicle whose transmission controller
carries out a gear selection and a gear shift. A new gear is
determined during the gear selection by reference to gear shift
characteristic curves stored in a characteristic diagram, and a
gear shift instruction, by which a gear shift is triggered, is
generated as soon as a working point of the drive train exceeds a
gear shift characteristic curve. If it is possible to shorten the
gear shift time required for a gear shifting operation, on one
hand, the gear shift comfort for the driver is increased and, on
the other hand, it is possible to improve the sporty
characteristics of the motor vehicle.
German Published, Non-Prosecuted Patent Application DE 195 33 305
A1 (D2) discloses an automatic transmission based on the object of
enabling the driver to make interactive intervention by which the
information regarding the transmission behavior that the driver is
currently dissatisfied with is transmitted to the control unit of
the transmission. The gear shift tendency or the dynamic behavior
of an operating point referred to the gear shift characteristic
curves of a characteristic diagram are used to carry out a
premature gear shift. The gear shift is not carried out shortly but
is, instead, brought forward, at the driver's request.
German Published, Non-Prosecuted Patent Application DE 196 26 193
A1 (D3) discloses a device for controlling programmed automatic
variable transmissions for motor vehicles. The control device is
composed of an electronic programmed circuit and a multiplicity of
sensors that are connected thereto and that supply the circuit with
a multiplicity of signals that influence the selection of the
driving positions of the automatic transmission. The signals
originate from the chassis and from the engine, and additional
signals are generated manually by the driver. Further signals that
cannot be influenced by the driver sense the physical conditions of
the driver. Examples of such conditions are the transpiration rate,
the posture in the seat, and the pulse rate, and they are,
therefore, physical functions that can change in a stressful or
hazardous situation.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method
for controlling an automatic transmission and controller suitable
for such a method that overcomes the hereinafore-mentioned
disadvantages of the heretofore-known devices and methods of this
general type and that shorten the gear shift time required for a
gear shifting operation.
With the foregoing and other objects in view, there is provided, in
accordance with the invention, a method for controlling an
automatic transmission in a drive train of a motor vehicle having a
transmission controller selecting and shifting gears of the
transmission, including the steps of determining a new gear during
a gear selection by referring to a gear shift characteristic curve
stored in a characteristic diagram, generating a gear shift
instruction to trigger a gear shift as soon as a working point of
the drive train exceeds a corresponding point on the gear shift
characteristic curve, determining, with the transmission
controller, a new gear expected to be engaged shortly and carrying
out an initial phase of the gear shift when the new gear differs
from the currently engaged gear and as soon as the working point
exceeds a pre-defined distance from the gear shift characteristic
curve, and completing a gear shift as soon as the gear shift
instruction has been generated.
The transmission controller determines the new gear and carries out
the initial phase of the gear shifting operation as soon as the
working point drops below a predefined distance from a gear shift
characteristic curve stored in the characteristic diagram, and the
gear shift instruction to trigger the gear shift is generated as
soon as the working point of the drive train exceeds the
corresponding gear shift characteristic curve.
The advantages of the invention are, inter alia, the fact that the
initial phase of the gear shifting operation remains completely
unnoticed by the driver. If a predetermined gear that has been
determined by the transmission controller as a gear that is
expected to be engaged shortly is then not engaged for whatever
reason, the lack of engagement does not adversely affect the gear
shift comfort in any way.
In accordance with another mode of the invention, preselection
characteristic curves running at the pre-defined distance from the
individual gear shift characteristic curves are stored in the
characteristic diagram.
In accordance with a further mode of the invention, a distance
between the preselection characteristic curves and the gear shift
characteristic curves is calculated as a function of a transmission
type.
In accordance with an added mode of the invention, a distance
between the preselection characteristic curves and the gear shift
characteristic curves is calculated as a function of a transmission
type during ongoing operation.
In accordance with an additional mode of the invention, a gear
shift to a gear determined as being expected to be engaged shortly
is prohibited if a dynamic correction of the gear shift instruction
has taken place.
In accordance with yet another mode of the invention, the
prohibited gear shift is carried out as soon as the dynamic
correction of the gear shift instruction is eliminated.
In accordance with yet a further mode of the invention, the
suppressed new gear is set as being the new gear to be engaged
shortly.
In accordance with yet an added mode of the invention, an expected
gear shift instruction is predicted by analyzing, in a manual
driving mode, a behavior of a driver of the motor vehicle
characteristic of a driving style.
With the objects of the invention in view, there is also provided a
method for controlling an automatic transmission in a drive train
of a motor vehicle having a transmission controller selecting and
shifting gears of the transmission, including the steps of
determining a new gear during a gear selection by referring to a
gear shift characteristic curve stored in a characteristic diagram,
generating a gear shift instruction to trigger a gear shift as soon
as a working point of the drive train exceeds a corresponding point
on the gear shift characteristic curve, determining, with the
transmission controller, a new gear expected to be engaged shortly
and carrying out an initial phase of the gear shift as soon as the
working point exceeds a pre-defined distance from the gear shift
characteristic curve, and completing a gear shift as soon as the
gear shift instruction has been generated.
With the objects of the invention in view, in an automatic
transmission of a motor vehicle, the transmission having gears,
there is also provided a transmission controller for controlling a
transmission ratio, including a characteristic diagram memory
storing transmission ratios to be set as a function of a torque and
a variable functionally associated with a speed of the vehicle,
gear shift characteristic curves, and preselection characteristic
curves lying at a predetermined distance from said gear shift
characteristic curves, and a processor programmed to signal an
expected new gear to the transmission and to prepare a gear
shifting operation when a working point overshoots said
preselection characteristic curves and to trigger a gear shifting
operation when the working point of the motor vehicle overshoots
the gear shift characteristic curves.
In accordance with a concomitant feature of the invention, there
are provided a gear selector circuit for determining a new gear of
the transmission, said gear selector circuit connected to said
processor, and a transmission control unit connected to said
processor and to said gear selector circuit, said transmission
control unit receiving a new gear signal, preparing a gear shifting
operation, and carrying out a gear shift to the new gear as soon as
the new gear determined by said gear selector circuit differs from
a currently engaged gear.
Other features that are considered as characteristic for the
invention are set forth in the appended claims.
Although the invention is illustrated and described herein as
embodied in a method for controlling an automatic transmission and
controller suitable for such a method, it is, nevertheless, not
intended to be limited to the details shown because various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims.
The construction and method of operation of the invention, however,
together with additional objects and advantages thereof, will be
best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatical illustration of a motor vehicle drive
train with a controller for an automated manual shift transmission
according to the invention;
FIG. 2 is a block circuit diagram of signals exchanged between the
transmission controller and the transmission in the method
according to the invention;
FIG. 3 is a graph indicating a gear shift characteristic diagram
used in the method according to the invention;
FIG. 4 is a graph of a time profile of a plurality of instruction
signals in the method according to the invention;
FIG. 5 is a block circuit diagram of a gear shift control unit of a
transmission controller according to the invention;
FIG. 6 is a graph of a time profile of a plurality of instruction
signals in another example of a method according to the invention;
and
FIGS. 7 and 8 are flow charts of a program executed in the method
according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the figures of the drawings in detail and first,
particularly to FIG. 1 thereof, there is shown a motor vehicle
drive 1 having--insofar as it is significant for the present
invention--the following components: an engine 2, a clutch 3, a
clutch actuator (also referred to below as actuator element or
actuator drive for the clutch) 4, an automatic transmission 5, a
transmission actuator 6, an electronic transmission controller 8
for the actuator element 4 and the transmission actuator 6, and an
engine controller 9. The transmission controller 8 is connected to
the actuator element 4 by control and signal lines 10 and to the
transmission actuator 6 by control and signal lines 11.
The actuating element 4 can be embodied as an electromotively
driven actuator or as a hydraulically driven actuator. In the
exemplary embodiment described herein, a hydraulic actuator element
4 is used that is connected to the clutch 3 by a force transmitting
configuration 12 that is embodied for example as a pressure line.
The transmission controller 8 contains, inter alia, a processor 16
connected to a characteristic diagram store or memory 13 on which
details will he given below. It is connected by a multiple data
line or a data bus 14 to the engine controller 9 and by data lines
or a databus 15 to a plurality of sensors that are disposed in the
motor vehicle in a conventional fashion at various points (engine,
transmission, brakes etc.) and are indicated by a block 17.
In the present exemplary embodiment, the transmission 5 is embodied
in the motor vehicle drive 1 as an automatic transmission. However,
it may also be embodied as an automated manual shift transmission
(ASG) that corresponds structurally to a conventional manual shift
transmission in which, however, the gears are shifted
automatically, and the clutch is activated automatically.
A gear shifting operation in an automatic transmission is generally
triggered and controlled by an electronic transmission controller
that is illustrated in FIG. 2 as a block 20. This operation can be
structurally divided into the selection of the suitable gear, which
is carried out in a gear selector (unit) 21, and into the control
of the transmission 22, in particular, during a gear shift, which
is carried out in a transmission control unit 24.
A gear shift is implemented, for example, by a new, subsequent gear
gp_nxt_cmd being determined by the gear selector 21. If the gear
differs from the currently engaged gear gp, the difference is
interpreted by the transmission control unit 24 as a gear shift
instruction and a shift to the next gear is carried out in the
transmission 22. The gear shifting operation is triggered in that
either a gear shift characteristic curve is exceeded in an
automatic driving mode or a corresponding instruction is given by
the driver in a manual driving mode by a switch or selector
lever.
The gear shift is divided into various phases whose configuration
depends, in particular, on the respective embodiment of the
automatic transmission. In an initial phase, actions for preparing
the gear shift operation are already carried out in the
transmission but the transmission ratio and the torque at the
wheels remain unchanged. The initial phase is unnoticed by the
driver. After the initial phase, the actual shifting begins, that
is to say, the gear shift operation during which the transmission
ratio and the torque at the wheels is changed.
The central feature here is to determine, before the actual gear
shift command, that is to say, a change in the instruction
gp_nxt_cmd, that gear gp_pct1_cmd which is expected to be engaged
in the near future. If the predetermined gear differs from the
currently engaged gear gp, the initial phase of a gear shifting
operation is immediately begun. The gear shifting operation that is
begun is then continued and completed, if the actual gear shift
command, that is to say, the instruction gp_nxt_cmd, occurs.
As a result of the division into two gear shift phases and the
preparation of the next gear, the required gear shift time can be
considerably shortened, and the comfort of the driver or the
sportiness of the vehicle can, thus, be increased. If the
predetermined gear does not correspond to the actual gear shift
command, the initial phase that is already initiated--without being
noticed by the driver--is aborted and the actually required gear
shift is carried out as soon as it becomes current.
The actual gear shift instructions are advantageously generated by
an intelligent adaptive transmission controller developed by the
assignee of the instant application (see, for example, German
Published, Non-Prosecuted Patent Application DE 196 37 210 A1,
corresponding to U.S. Pat. No. 6,188,945 to Graf et al., which is
hereby incorporated by reference) that has also become recognized
under the name SAT transmission controller. The present
transmission controller and the associated control method can be
integrated very well into the gear shift and program structure of a
SAT transmission controller.
The two-phase control method according to the invention with
predetermination of the new gear is also referred to below for
short as "gear preselection". A distinction is made here between a
gear preselection in the automatic mode, a gear preselection in the
automatic mode with dynamic correction, and a gear preselection in
the manual mode, that is to say, when there is a desired gear input
by the driver.
The gear preselection in the automatic driving mode is explained by
a (gear shift) characteristic diagram that is shown in FIG. 3 and
in which the working point AP of the motor vehicle
drive--characterized by the current accelerator position FP, the
engine torque Mmot, the wheel torque Mrad, or the remaining wheel
torque Mresrad--is represented as a function of the speed v of the
vehicle or a variable that is proportional thereto. For the sake of
better clarity, only two characteristic diagrams: a shift-down
characteristic curve 26 and a shift-up characteristic curve 27 are
shown in the characteristic diagram. If the working point AP
exceeds the shift-up characteristic curve 27, a shift-up is
triggered in a conventional fashion; if it drops below the
shift-down characteristic curve a shift-down operation is
triggered.
The characteristic diagram also contains here what are referred to
as preselection characteristic curves that run at a predefined
distance from the respective characteristic curve and of which only
two are illustrated (shown by broken lines) for the sake of
explanation: a preselection shift-down characteristic curve 28 and
a preselection shift-up characteristic curve 29.
The preselection function of the transmission controller then lies
in the fact that even before the working point AP exceeds a
shift-up or shift-down characteristic curve, the next gear is
signaled and the transmission is prepared for the imminent gear
shift operation.
Distances 30 and 31 of the working point AP from the characteristic
curve 26 or 27 are decisive for the prediction of the next gear. If
one of these distances exceeds a critical dimension, which is
referred to as the preselected distance 30 or 31, a preselection of
the next or new gear is made. The preselection characteristic
curves 28 and 29 run at the distance 30 and 31 from the respective
characteristic curve 26 or 27. The distances 30 and 31 depend on
the driving speed and on the vehicle type. They are predefined for
each point of the associated gear shift characteristic diagram. In
an exemplary embodiment, the distance at an average driving speed
corresponds to a speed change of .DELTA.v=5 km/h.
If the distance 31 between the working point AP and the shift-up
characteristic curve 27 is undershot, the transmission is prepared
for an imminent shift-up operation, and when the distance 30 from
the shift-down characteristic curve 26 is undershot a shift-down
operation is prepared. To ensure reliable operation and to adapt
the prediction to the various types of transmission (double clutch
transmission, planetary gear transmission, automated manual shift
transmission), the distance is continuously calculated in real-time
operation.
The gear preselector in the automatic driving mode with dynamic
correction will now be explained with reference to instruction
signal profiles shown in FIG. 4.
In the aforementioned SAT transmission controller, a gear change
from a current gear n to a new gear n+1, which was supposed to be
statically triggered when the signal gp_new exceeded a gear shift
characteristic curve at a time t.sub.1, is prohibited for a certain
time under particular driving conditions. Such a configuration
constitutes a dynamic correction that is brought about by an
occurrence of a signal st_cor_dyn. As a result, the dynamically
corrected gear gp_dyn=n is engaged. The gear shift to the gear n+1
does not take place until this signal is eliminated again at a time
t.sub.3, that is to say, assumes the status "0" again. A gear that
is conventionally calculated by the transmission controller 8, in
particular, by a SAT transmission controller, that is to say,
without using the method according to the invention, is referred
herein as "static".
In such a case, the suppressed new gear is used directly as a gear
preselection. In the corresponding initial phase between the times
t.sub.1 and t.sub.2, a second shaft in the transmission is
synchronized, that is to say, the engine is accelerated from the
rotational speed corresponding to the gear n to the rotational
speed of n+1. After the dynamic correction is eliminated, the
suppressed gear is passed on and the gear shift command gp_nxt_cmd
becomes effective.
The gear preselection in the manual driving mode will now be
explained with reference to a gear shift control unit 32 shown in
FIG. 5. The unit 32 includes an evaluation logic 33, a computing
and logic element 34 or arithmetic unit, a memory 35, a
plausibility circuit 36, a gear selector circuit 38, and a gear
preselector circuit 39 that are connected to one another by the
data and signal lines shown in the drawing. The normal new gear is
calculated--as defined in the SAT transmission controller--and
output as a gear shift instruction gp_nxt_cmd in the gear selector
circuit 38. The gear shift instruction gp_nxt_cmd is referred to
here, as mentioned above, as a steady-state gear shift
instruction.
During the gear preselection in the manual mode, it is more
difficult to predict a gear shift instruction to be expected from
the driver. One possibility is to analyze the typical behavior of
the driver to be able to make an appropriate prediction in similar
situations. Another possibility is to evaluate information that is
supplied by sensors in or on the vehicle and that enables a gear
shift request to be detected.
For such a purpose, all the gear shift operations triggered by the
driver and the associated driving conditions are analyzed by an
evaluation logic 33 and a driver characterization that is derived
therefrom is stored in a memory 35. The evaluation logic 33
continuously monitors the gear shift behavior of the driver and
stores all the data necessary for analysis before and after the
actual driver intervention: data relating to the route, from a
driver information system, relating to the rotational speed of the
engine, the gear request, the accelerator pedal position, the speed
of the vehicle, the inclination of the carriageway, the driving
style (is determined by a fuzzy logic system during SAT
transmission control), and the position of the gear shift selector
lever.
The data is fed to the evaluation logic 33 through signal inputs
40. It is supplied partly by the sensors 17 and partly by the
transmission controller 8. A gear request that is input through a
gear shift lever, a selector lever, a gear shift rocker, or the
like is fed through an input line 41 to the arithmetic unit 34.
Here, for example, the following aspects are examined: how
frequently was each gear engaged (manually or automatically)? For
how long was each gear held on average? At what rotational speeds
and at what speed of the vehicle was the corresponding gear
engaged? What additional operational variables (activation of the
brakes, gradient of the accelerator pedal, load value or driver
value etc.) are characteristic of the driving style? How frequently
was the prediction of the next gear correct or incorrect?
The cause of the gear shift operation can be determined from the
pre-history before a gear shift operation and the observation of
the situation after the gear shifting. The logic linking of the
data is carried out in the computing and logic unit 34. If all the
gear shift operations that have been carried out have been
classified according to the observed situations, an empirical
driven profile can be stored in the memory 35.
From the driver profile stored in the memory 35 and the data in the
evaluational logic unit 33, it is possible to draw conclusions
about the new gear that the driver is expected to engage. The
calculation is carried out in the gear preselector circuit block or
module 39 and a corresponding instruction gp_pct1_cmd signaling
what is expected to be the next gear is output.
Gear shifting interventions of the driver that cannot be associated
with any conventional driving situation are filtered out by the
plausibility circuit 36 and not included in the storage process.
The driver profile that is determined can be stored in a personal
memory for each individual driver and it can be used as an initial
data record after the vehicle is started again.
In addition, the evaluation of sensor signals and information from
other electronic systems, in particular, from navigation systems,
provides the possibility of predicting gear shift requests of the
driver or supporting the information acquired from the driver
characteristic described above. Examples of such possibilities are:
The movement of the driver's hand to the gear shift lever or other
operating controls for shifting gear can already be detected at an
early time by movement or proximity sensors. Weight sensors in the
driver's seat can also give an indication of a movement toward the
gear shift lever. The signal of a gear shift lever is usually
initially debounced, that is to say, read out repeatedly before it
is interpreted by the electronic transmission controller as an
ensured gear shift instruction. However, even the first occurrence
of the signal can be used to predict a new expected gear. Color and
distance sensors provide information on the current traffic
situation by the possibility of detecting brake lights or states of
traffic lights. With knowledge of the traffic situation, it is
possible to predict probable shift-up and shift-down operations.
Information relating to the traffic situation and terrain can be
obtained through GPS navigation systems. Shift-up and shift-down
operations that were expected to become necessary can also be
predictably determined therefrom.
It is decisive to determine the predicted future gear even before
an actual gear shift command to the automatic transmission 5 is
triggered so that it is possible to begin the initial phase of a
gear shift immediately and, as a result, the gear shift time can be
significantly shortened.
To achieve the response time improvement, in the automatic driving
mode, the distance between the current working point and a gear
shift characteristic curve is determined and used to predetermine
the future gear and to determine the most suitable time for it to
be output. When a dynamic correction is present, the predetermined
gear can be transferred to directly from it.
In the manual driving mode, the future gear and the time of the
actual gear shift command can be determined by analyzing the
behavior of the driver as a function of the current driving
situation. The use of sensors or navigation systems also permits
the future gear to be determined and also the plausibility of the
data from the driver's analysis to be tested.
Examples of the application of the method according to the
invention for various types of transmissions are described below
with reference to FIG. 6. The time profile of the preselection
instruction gp_pct1_cmd that prepares the gear shift from a gear n
to the next gear n+1, and of the gear shift instruction gp_nxt_cmd
that triggers the gear shift is illustrated in the upper part of
the diagram.
In the case of double clutch transmissions, such as those disclosed
in the ATZ Automobiltechnische Zeitschrift 101 (1999) 5, pages
350-357, it is appropriate to leave the idling or neutral position
engaged on the second transmission shaft for as long as possible to
keep the losses in the transmission low. The preparation of the
second transmission shaft for the gear shift can be kept as short
as possible by the prediction of the new gear.
The preparation is expediently started such a short time before the
actual gear shift that when the shift-up or shift-down
characteristic curve is reached the gear on the second transmission
shaft (shaft 2 in the lower part of FIG. 6) is just engaged. For
this, the extrapolation of the current working point is displaced
so far into the future that there is still sufficient time to
prepare the second shaft for the new gear. This begins at the time
t.sub.1.
The gear preselection must be made a time period .DELTA.t before
the actual gear decision by the gear shift characteristic curves.
The time period .DELTA.t is composed of a synchronization time
ST=t.sub.2 -t.sub.1 for the gear shift and an overlapping time
UT=t.sub.3 -t.sub.2. It also depends on the dynamics of the working
point.
.DELTA.=f (gear shift time, overlapping time, dynamics of the
working point)
In planetary gear transmissions, the initial phase of a gear shift
operation includes reducing the pressure at the opening clutch or
brake without slip occurring and increasing the pressure at the
clutch or brake that is to be closed such that the contact point is
almost reached. The latter is usually achieved by a rapid filling
operation.
In planetary gear transmissions, the duration of this initial phase
is, however, of such a length that a significant delay between the
manual triggering of a gear shift operation and the change in the
transmission ratio that can be perceived by the driver occurs. If
the method according to the invention is used in a planetary gear
transmission and the initial phase of the gear shift operation
described above is carried out before the actual gear shift
command, the gear shift time and, in particular, the delay after
the manual gear shift command can be significantly reduced. The
behavior of the vehicle is significantly more sporty.
In automated manual gear shift transmissions, the predetermination
of a new gear can be used to reduce the contact force between the
clutch plates just before the actual gear shift operation such that
slip is just avoided, that is to say, the clutch capacity is
adapted to the torque to be transmitted. As a result of such a
measure, it is possible to further reduce the gear shift times even
in vehicles that have a sporty configuration and decidedly short
gear shift times.
In contrast to the above, the conventional procedure is to adapt
the clutch capacity to the torque to be transmitted at all times,
as a function of the configuration of the clutch and associated
with an increased expenditure of energy. In customary embodiments
of the clutch for automated manual gear shift transmissions, it is
necessary, in fact, to apply energy to open the clutch.
A program that can be seen in FIGS. 7 and 8 and that is executed in
the method according to the invention includes the following steps
(each designated by S). S1: A load factor ld_f and a sportiness
factor dr_f of the motor vehicle are calculated in the transmission
controller (of the SAT type). S2: The new static gear gp new is
calculated. S3: A gear decision that is input manually by the
driver can be taken into account here. S4: The preselection
distance for a shift-down operation is calculated. S5: The
preselection distance for a shift-up operation is calculated. S6: A
dynamic correction is calculated. S7: There is an inquiry to
determine whether or not the dynamic correction is active and the
program proceeds to step if S8 if the answer is yes and to step S11
if the answer is no. S8: The preselected gear is set to be equal to
the new (static) gear gp_new. S9: The target gear gp_nxt_cmd is set
to be equal to the current gear. S10: The gear shift is started.
S11: There is an inquiry to determine whether or not the working
point has dropped below the shift-down characteristic curve and the
program proceeds to step if S12 if the answer is yes and to step
S15 if the answer is no. S12: The preselected gear is set to be
equal to the current gear minus 1. S13: The target gear gp_nxt_cmd
is set to be equal to the new (static) gear gp_new. S14: The gear
shift is started. S15: There is an inquiry to determine whether or
not the working point has exceeded the shift-up characteristic
curve and the program proceeds to step if S16 if the answer is yes
and to step S19 if the answer is no. S16: The preselected gear is
set to be equal to the current gear plus 1. S17: The target gear
gp_nxt_cmd is set to be equal to the new (static) gear gp_new. S18:
The gear shift is started. S19: The preselected gear is set to be
equal to the current gear or the idling speed. S20: The target gear
gp_nxt_cmd is set to be equal to the new (static) gear gp_new. S21:
The gear shift is started.
After the steps S10, S14, S18, or S21, a gear shift is terminated
in each case. The program will run through again for a subsequent
gear shift.
* * * * *